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Showing papers in "Theoretical and Experimental Plant Physiology in 2018"


Journal ArticleDOI
TL;DR: In this paper, the role of proline per se and in combination with water deficit on the production of phenolic compounds in leaves of transgenic tobacco plants (Nicotiana tabacum) with increased proline content was evaluated.
Abstract: Proline metabolism has been proposed to play an important role in activating the shikimic acid pathway for increased secondary metabolites production in plants. Here we evaluated the role of proline per se and in combination with water deficit on the production of phenolic compounds in leaves of transgenic tobacco plants (Nicotiana tabacum) with increased proline content. For this, an experiment was carried out under greenhouse conditions using three genotypes (transgenic events E1 and E2 constitutively expressing the mutant gene VaP5CSF129A and an untransformed control) and two levels of water regimes (100% and 30% of soil field capacity). Total phenolics, proline, activities of glucose-6-phosphate dehydrogenase (G6PDH) and phenylalanine ammonia-lyase (PAL), and lignin were measured in the leaves. As expected, a reduction in biomass was observed in all genotypes under drought conditions and the maximum accumulation of proline occurred in transgenic plants in both water regimes. Under irrigated conditions, phenolics were only slightly superior in leaves of the transgenic event E2, while both events presented a noticeable increment in total phenolics and PAL activity under water deficit. Lignin biosynthesis also increased in all genotypes in response to drought stress, but it was more noticeable in the transgenic plants. On the other hand, the activity of the G6PDH enzyme was consistently lower in the transgenic plants in both irrigated and water-deficit condition. Our results do not confirm the association between de novo proline synthesis and the stimulation of G6PDH to produce phenolics.

37 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of exogenous salicylic acid (SA) added to the nutrient solution on the growth parameters and the functions of the photosynthetic apparatus of rice plants under cadmium (Cd) stress was investigated.
Abstract: The present study was conducted to investigate the effect of exogenous salicylic acid (SA) added to the nutrient solution on the growth parameters and the functions of the photosynthetic apparatus of rice plants under cadmium (Cd) stress. Our investigations have shown that 10 µM SA has an optimal effect in rice plants grown hydroponically. Pulse amplitude modulated chlorophyll fluorescence, low-temperature chlorophyll fluorescence, oxygen evolution (measured with Clark-type and Joliot-type electrodes) and P700 photo-oxidation measurements were carried out to assess the effect of SA on the activity of the photosynthetic apparatus. The levels of three important parameters associated with oxidative stress (hydrogen peroxide, lipid peroxidation and proline content) were measured. The application of low concentration of SA significantly decreased the levels of hydrogen peroxide, lipid peroxidation and proline under Cd stress. The results revealed that low concentration of SA, applied in plants exposed to 150 µM CdCl2, significantly improves plant growth, photochemical activities of both photosystems, the electron flow from QA to plastoquinone, energetic distribution between pigment-protein complexes and the kinetic parameters of oxygen-evolving reactions. This study suggests that exogenous application of 10 µM SA through the rooting medium has a protective effect against Cd toxicity in rice plants. The possible molecular mechanisms involved in the defence effect of SA on the function of photosynthetic apparatus are discussed.

29 citations


Journal ArticleDOI
TL;DR: In this article, the role of the superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), and APX enzymes in Salvinia molesta tolerance to AsIII was investigated.
Abstract: Antioxidant enzymes are important components in the defense against arsenic (As) stress in plants. Here, we tested the hypothesis that Salvinia molesta, an aquatic fern, counteracts the harmful arsenite (AsIII) effects by activating scavenging reactive oxygen species (ROS) enzymes. Thus, our objective was to investigate the role of the superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), and ascorbate peroxidase (APX) in S. molesta tolerance to AsIII and indicate the use of this plant in remediation of contaminated water. Plants were grown in nutrient solution at pH 6.5 and exposed to 0, 5, 10, or 20 µM AsIII for 96 h (analyses of As absorption, mineral nutrient content, and relative growth rate) and for 24 h (analyses of oxidative stress indicators and enzymatic antioxidant defenses). In the floating leaves, there was a greater basal activity of the antioxidant enzymes and less accumulation of As than in submerged leaves. The submerged leaves, which function as roots in S. molesta, accumulated more As than floating leaves, and SOD and CAT activities were inhibited. Thus, there was a greater production of ROS and oxidative stress. Our results show that S. molesta presents enzymatic antioxidant defenses to alleviate AsIII toxicity and are more effectives in the floating leaves. These results are important to elucidate the AsIII tolerance mechanisms in S. molesta and the possibility of their use in contamined water phytoremediation. Additional studies exposing plants to more prolonged stress and using AsIII concentrations closer to those found in contaminated environments will confirm this claim.

21 citations


Journal ArticleDOI
TL;DR: Genotypic differences in Al tolerance in four Urochloa forage grasses are evaluated, suggesting that in the genotypes that are more tolerant to Al there is maintenance of metabolic activities, including upregulated and efficient antioxidant activity, root growth, LA growth and biomass yield.
Abstract: Forage grasses belonging to the Urochloa (Brachiaria) genus present tolerance to Al toxicity, however there are intra- and interspecific differences among the species, which in turn should be better depicted. Here we evaluate genotypic differences in Al tolerance in four Urochloa (U. decumbens cultivar Basilisk; U. brizantha cultivar Marandu; U. brizantha cultivar Piata and U. brizantha cultivar Xaraes) cultivated in nutrient solution, during growth and regrowth. We analyzed the effect of Al uptake on epidermal and cell membrane damage, and lipid peroxidation in shoots and roots. Exposure of genotypes to Al concentration up to 1.33 mmol L−1 led to different degrees of shoot yield, mainly during the growth period. Increased Al concentration decreased dry matter production in shoots and roots, reduced leaf area (LA), relative root growth, increased Al accumulation in the roots and root-to-shoot Al translocation, notably during the first growth period. However, Al translocation from roots to shoots augmented massively in all genotypes, during the regrowth. Plant roots exposed to Al were damaged, exhibiting ruptures in the epidermis and reduced number of root hairs. Lipid peroxidation in shoots ranged in all genotypes exposed to Al, however, the oxidative stress was 2–5 times higher in shoots than in roots, notably in Marandu that accumulated 95% more Al than U. decumbens. This suggests that in the genotypes that are more tolerant to Al there is maintenance of metabolic activities, including upregulated and efficient antioxidant activity, root growth, LA growth and biomass yield.

20 citations


Journal ArticleDOI
TL;DR: In this paper, the influence of soil temperature on the ecophysiology of two plant species with different mechanisms of CO2 assimilation was investigated: maize (C4) and bean (C3).
Abstract: Extreme soil temperatures are the main limitation to the expansion of agriculture. In Brazil, this also affects the second crop, which is usually performed every year. We investigated the influence of soil temperature on the ecophysiology of two plant species with different mechanisms of CO2 assimilation: maize (C4) and bean (C3). The plants, in the vegetative phase, were subjected to three soil temperatures: low (9–12 °C), ambient (25–30 °C), and high (27–42 °C). Our results indicate that both low and high soil temperatures negatively affected the photosynthetic process of the studied plants. The reduction of CO2 assimilation rates under low soil temperature was mainly due to stomatal closure, while under high soil temperatures, it was related to decreased carboxylation rates. Short-term exposure to extreme soil temperatures affects the root system growth and, in maize plants, leads to impaired shoot dry mass accumulation. Besides that, stresses caused by high soil temperature reduced the relative water content of the leaves, causing an increase in leaf temperature and cells rupture.

19 citations


Journal ArticleDOI
TL;DR: It is concluded that BRs do not interfere with the senescence of the youngest leaf (L1) but in older leaves (L3) BRWC maintains the leaves greener and attached to the plant for a longer time when compared to the leaves from the other treatments.
Abstract: The application of brassinosteroids (BR) is associated with increased tolerance to various stresses such as those induced by pathogens, temperature, salinity and drought. Here, we studied the influence of BRs analogues on the leaf senescence of papaya juvenile plants. The objective was to determine whether BRs affect plant growth and leaf senescence by promoting or inhibiting the degradation of chlorophyll and/or leaf abscission. Two-month-old plants were divided into five treatments: C (control without BR application); BRWC (BR applied in the whole canopy); BRL1 (BR applied in the youngest fully expanded leaf, L1); BRL2 (BR applied in L2 which is the secondly more mature leaf in relation to L1) and BRL3 (BR applied in L3 which is the third more mature leaf in relation to L2). We concluded that BRs do not interfere with the senescence of the youngest leaf (L1) but in older leaves (L3) BRWC maintains the leaves greener and attached to the plant for a longer time when compared to the leaves from the other treatments. BR application in whole-canopy increased the plant height, and it caused a delay in leaf senescence and, consequently, in leaf abscission. In addition, hyponastic leaves developed after BR-application in the whole-canopy. The senescence process and leaf abscission in papaya, stimulated by exogenous BRs, were directly related to leaf age.

17 citations


Journal ArticleDOI
TL;DR: It is observed that both nitrate starvation and root growth media modulate overall root system architecture, however, the ability of such modulation is genotype specific.
Abstract: Roots have significant impact on plants ability to adapt to different environmental constraints such as nutrient availability. They exhibit varied morphological responses to different nitrogen levels indicating its developmental plasticity in relation to nitrogen availability. In order to understand the genetic diversity in modulation of root architecture among diverse wheat genotypes in response to external root growth media and nitrate starvation, root system architecture parameters such as total toot size, main root size, lateral root size, 1st order lateral root number and 2nd order lateral root number were studied in 15 days old seedlings of twelve diverse wheat genotypes carrying different nitrogen use efficiency traits in three different root growth media i.e. hydroponic culture (HC), solid nutrient free (in terms of plant nutrients; vermiculite and perlite mixture; VPC) culture and soil culture (SC). We observed that both nitrate starvation and root growth media modulate overall root system architecture. However, the ability of such modulation is genotype specific. Further, the solid nutrient free media, in contrast to solution culture (HC), induced much pronounced effect on overall architecture indicating their nitrate foraging ability in natural soil condition. Among the two solid media, VPC has caused more exploratory root morphology in nitrate deficient condition. In general the effect of nitrate stress is more predominant in VPC followed by HC than SC. Among genotypes, NP846 and HS1097-17 were found to be most responsive towards nitrogen starvation condition and root growth media as far as root traits are concerned.

15 citations


Journal ArticleDOI
TL;DR: In this article, Gibberellic acid (GA3) was used to up-regulate the chloroplast lipid biosynthesis under salt disturbance in rice, and the results indicated that exogenous application of GA3 participates in up-regulation of chloroplayer lipid biosynthetic genes in rice.
Abstract: Alterations in membrane lipid composition lead to improved plant salt tolerance. Gibberellic acid (GA3) has also been widely reported to reduce growth inhibition induced by increased salinity. However, little is known about whether exogenous application of GA3 participates in up-regulation of lipid biosynthesis under salt stress. In this study, one of the major lipid biosynthesis genes in rice (Oryza sativa L. cv. Nipponbare), monogalactosyldiacylglycerol synthase (OsMGD) was found to be significantly up-regulated by GA3 treatment. Lipid analysis showed that after salt disturbance, the concentrations of all the measured lipids, including monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG) and phospholipid lipids + sulfoquinovosyl diacylglycerol (PL + SQDG) were decreased significantly. However, GA3 treatment prior to salt disturbance caused those lipids to remain at high levels, as well as preserving a high DGDG/MGDG ratio. The desaturation of DGDG (DBI) was also increased in GA3 pre-treatment plants as compared with no GA3 pre-treatment, primarily due to a decrease of 16:0 fatty acids and an increase of 18:3 fatty acids in DGDG. Plants pre-treated with GA3 prior to salt disturbance had higher dry weights than those without pre-treatment. The chlorophyll concentration was also higher in GA3 treated plants than in untreated plants under salt disturbance. Taken together, these results indicate that exogenous application of GA3 participates in up-regulation of chloroplast lipid biosynthesis under salt disturbance in rice.

13 citations


Journal ArticleDOI
TL;DR: Results obtained on the relationships between different plant attributes indicated that adaptation to acid soils and high temperatures is related to pollen viability, earliness, greater values of canopy biomass and better mobilization of plant reserves to the formation of pods and grains.
Abstract: The common bean (Phaseolus vulgaris L.) is a major food legume cultivated by smallholder farmers in the tropics of Latin America and eastern and southern Africa. Acid soil and high temperature limit its production. Here we quantify differences in agronomical, phenological and physiological performance of common bean lines in order to identify promising lines with adaptation to acid soils and high temperatures in the Amazon region of Colombia. A field study was conducted using a 6 × 6 Alfa Lattice design with four replications consisting of 30 genotypes and one control genotype (Calima) which was repeated six times in each block (with a total of 36 plots) to cope with the spatial variability within the experimental site. During the growing period of the crop, maximum and minimum average temperatures were 32 and 23 °C, respectively while the total precipitation was 933 mm and the soil was acidic with aluminum toxicity. Differences in agronomical (grain yield, canopy biomass, number of seeds and pods per area), phenological (days to flowering and days to physiological maturity) and physiological (biomass partitioning, photosynthetic ability and pollen viability) attributes among the genotypes tested were quantified. The results obtained on the relationships between different plant attributes indicated that adaptation to acid soils and high temperatures is related to pollen viability, earliness, greater values of canopy biomass and better mobilization of plant reserves to the formation of pods and grains. Two common bean lines (BFS 10 and NCB 280) were identified as better adapted to the combined conditions of acidic soil and high temperatures in the Amazon region of Colombia.

13 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that manipulation of gibberellic acid levels can influence plant biomass accumulation by modifying the internode length and, consequently, light capture efficiency.
Abstract: Plants are constantly subjected to light variations in the environment, and plant hormones are one of the intermediaries between environmental signals and physiological responses. Among these responses, gibberellins (GAs) promote physiological changes that regulate plant growth and development patterns. Morphological changes, such as internode length and light absorbance maximization, are likely to induce plant performance increases leading to biomass accumulation. In this context, the hypothesis tested herein was that manipulation of GA levels can influence plant biomass accumulation by modifying the internode length and, consequently, light capture efficiency, with direct effects on plant biomass accumulation rates evaluated by unit leaf rate and growth analysis. For this, tobacco plants were cultivated in high- and low- irradiance environments under different gibberellic acid (GA3) and paclobutrazol (PAC, a GA biosynthesis inhibitor) concentrations as a tool to manipulate the internode length and plant height. Dry matter accumulation was evaluated in response to light capture efficiency and interception, energy content and anatomical stem changes. The results obtained and supported by a principal component analysis indicate that GAs are capable of promoting phenotypic changes in plants grown in both high and low irradiance environments, and that they trigger responses related with biomass accumulation by maximizing light capture performance in response to internode length in tobacco plants. The data presented herein emphasize that GAs are essential in promoting growth and biomass accumulation, especially in low irradiance environments.

12 citations


Journal ArticleDOI
TL;DR: The results showed that the Orn index, including quantitative and qualitative aspects, should be recommended to evaluate salinity tolerance in ornamental species, especially for garden flowers of commercial interest.
Abstract: The traditional methods to evaluate salt tolerance of plants use mainly data of growth and crop productivity. In the case of ornamental plants it is also essential to evaluate the effects on the visual quality of the plants, since the beauty in the acquisition of an ornamental plant is not always associated with its size. So, we tested a new method to assess salt tolerance of four ornamental species, comparing with traditional ones. The experimental design was in completely randomized blocks, in a 10 × 4 factorial arrangement, with four replications, ten levels of electrical conductivity of irrigation water—ECw (0.5, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 8.0, 10.0, 12.0 dS m−1) and four ornamental species (Catharanthus roseus, Allamanda cathartica, Ixora coccinea and Duranta erecta). Two salinity tolerance assessment methods, which are based only on quantitative growth data, were evaluated and compared with a new method, named ornamental index (Orn index) that considers growth data and visual analysis. Our results showed that the two traditional assessment methods converge to indicate I. coccinea and D. erecta, respectively, with higher and lower capacity to grow under salt stress. However, these methods present clear differences in the results between quantitative data (biomass production) and qualitative analyses (flower production and overall plant appearance). The new method (Orn index) adequately separated the four ornamental species according to their tolerance to salinity, as follows: I. coccinea (moderately tolerant), C. roseus and D. erecta (moderately sensitive), and A. cathartica (sensitive). Hence, the Orn index, including quantitative and qualitative aspects, should be recommended to evaluate salinity tolerance in ornamental species, especially for garden flowers of commercial interest.

Journal ArticleDOI
TL;DR: In this article, the salinity tolerance of wild beets was evaluated during seed germination and early seedling development of three Portuguese wild beet ecotypes [Comporta (CMP), Oeiras (OEI), Vaiamonte (VMT), and one sugar beet cultivar (Isella) was evaluated, with 98% (± 2%) of glomerules germinating in 200mM NaCl after 14 days of scarification.
Abstract: Sugar beet (Beta vulgaris L.) high yields have been achieved through irrigation and this crop is described as coping with mild salinity (40–120 mM NaCl). However, during seed germination, sugar beet is salinity sensitive and soil salinity should not exceed 3 dS/m. Wild beets, ancestors of sugar beet, are naturally able to germinate and grow in saline environments. Salinity tolerance during germination and early seedling development of three Portuguese wild beet ecotypes [Comporta (CMP), Oeiras (OEI), Vaiamonte (VMT)] and one sugar beet cultivar (Isella) was evaluated. Concerning germination, VMT outperformed all the other beets, with 98% (± 2%) of glomerules germinating in 200 mM NaCl after 14 days of scarification. However, in 500 mM NaCl, only CMP was able to initiate and maintain radicle emergence, though in a very small extension (< 3%). On the basis of the relative salinity tolerance index, CMP is the less affected by salinity, despite reduced seedling growth and biomass. Since cotyledons length and membrane proteins abundance were negatively affected by salinity, the hypothesis was raised that membranes functionality, including the photochemical multiprotein complexes, was compromised. To test this hypothesis, a blue-native two-dimensional electrophoresis was applied to CMP seedlings. In the cotyledonary leaves, complexes LC1 and LC4 and several components of LC2, LC5, LC6 complexes were negatively affected by salinity. The components of the complexes of photosystem I and ATP synthase were less abundant what points out to a lower cotyledon capacity for ATP synthesis and ferredoxin reduction. Lower availability of ATP and reduced ferredoxin imply reduced photosynthetic assimilation and, therefore, lower carbon availability for growth.

Journal ArticleDOI
TL;DR: In this article, aqueous methanol extracts of C. mimosoides leaves and stems were used to investigate the phytotoxicity of the leaves against the growth of different types of plants.
Abstract: Caesalpinia mimosoides (Fabaceae) has been used as a folk medicine and reported to have pharmacological properties. However, the phytotoxicity of C. mimosoides has not yet been studied. Therefore, the phytotoxic activity of C. mimosoides leaf and stem extracts was evaluated against the growth of dicotyledonous and monocotyledonous plants. Aqueous methanol extracts of C. mimosoides leaves and stems exhibited inhibitory effects on the growth of all the test plants. The growth of the test plants decreased with the increase of concentrations of the extracts. Comparison of the concentrations required for 50% growth inhibition (I50 values) indicates that the leaf extracts had more inhibitory effects than the stem extracts. Thus, the active substances in the leaf extracts were purified using column chromatographic separations and a growth inhibitory substance was isolated and identified as methyl gallate by using spectral analysis. This study reports the first isolation of methyl gallate in C. mimosoides leaves. Methyl gallate at 10 mM completely inhibited the growth of cress shoots and inhibited its roots by 4.7% of control growth. At the same concentration, the shoots and roots of barnyard grass were inhibited by 84.2 and 1.7% of control growth, respectively. I50 values of methyl gallate for the growth of cress and barnyard grass ranged from 2.3 to 2.9 and 0.3 to 30.5 mM, respectively. The results suggest that methyl gallate may be responsible for the phytotoxic effects of C. mimosoides.

Journal ArticleDOI
TL;DR: In this paper, ascorbic acid (AA) concentrations above 30 mM caused strong cellular and oxidative damage indicated by decreased cell integrity and increased lipid peroxidation in leaves.
Abstract: Toxicity caused by high concentrations of ascorbic acid (AA) has been widely reported in animal cells but is scarcely described in plants. In this study, rice plants deficient (knockdown) in two chloroplast ascorbate peroxidases (APX7/8) and non-transformed (NT) were exposed to wide exogenous AA concentrations in the presence of low light and high light (HL). Reduced (ASC) and oxidized (DHA) ascorbate reached much higher concentrations in symplast compared to the apoplastic space, and high redox states were found in both cellular compartments. Exogenous AA concentrations above 30 mM caused strong cellular and oxidative damage indicated by decreased cell integrity and increased lipid peroxidation in leaves. These toxic effects were strongly enhanced by HL and, to a small extent, by deficiency of both chloroplastic proteins APX7/8. The combination of HL and high AA concentration induced a strong increase in H2O2, associated with decrease in the content of chlorophylls and carotenoids. High AA concentrations strongly induced stomatal closure and impairment in CO2 assimilation, in combination with decreased quantum efficiency of photosystem II (PSII) and PSI. We postulate that oxidative stress caused by AA toxicity in the presence of HL was induced by over-production of reactive oxygen species due to an imbalance between excess energy in the photosystems and low CO2 assimilation, which was related closely to strong decrease in stomatal conductance. In addition, high ASC levels might have acted as a pro-oxidant in the presence of high H2O2 concentrations, stimulating the Fenton reaction and contributing to the intensification of oxidative stress in rice leaves.

Journal ArticleDOI
TL;DR: In this paper, the effect of light quality on pepper plants' physiology during a period of water deficit was evaluated, and the results suggest that pepper plants grown under CFL radiation perform better, even under water deficit, possibly due to the more balanced light spectrum.
Abstract: The application of artificial light to improve crop production in greenhouses is widely used in the horticultural sector. In this study, we evaluated the impact of light quality on sweet pepper plants’ physiology during a period of water deficit. Pepper plants were cultivated in a climate chamber and exposed to three different light regimes; (compact fluorescent lamps [CFL], continuous intensity from light emitting diodes [LED] [LEDcont] and bell-like shape illumination schedule from LEDs [LEDday]). The effect of temporary water shortage under these light treatments on plant height, chlorophyll and proline concentration, the maximum efficiency of photosystem II (Fv/Fm), the electron transport rate (ETR), and the non-photochemical quenching (NPQ), were studied. In general, plants exposed to CFL showed higher growth rates as compared to those exposed to LED under well-watered conditions. However, the lighting source did not induce significant effects on plant growth and chlorophyll concentration during water deficit, even though proline concentration was higher in plants exposed to CFL and to drought when compared to those exposed to LEDcont and LEDday. LED radiation led to a higher ETR and an early onset of NPQ under water deficit, suggesting an activation of the cyclic electron transport. As outcome, plants grown under LEDcont showed the highest photochemical performance. Overall, the results suggest that pepper plants grown under CFL radiation perform better, even under water deficit, possibly due to the more balanced light spectrum.

Journal ArticleDOI
TL;DR: It is concluded that the mycorrhization of seedlings of ‘aroeira-do-sertão’ associated with P fertilization maximizes the production of total phenols and total foliar proteins, making the phytomass more attractive to the herbal industry and resulting in the use of P fertilizing.
Abstract: ‘Aroeira-do-sertao’ (Myracrodruon urundeuva Allemao; Anacardiaceae) is one of the most-used medicinal species by the population of northeastern Brazil and is on the list of plants threatened with extinction. In this context, alternatives that could contribute to reduced extractive use must be designed to establish crops of this species, which have high concentrations of metabolites. Inoculation with arbuscular mycorrhizal fungi (AMF) and the addition of phosphorus (P) to soil increases the production of primary and secondary metabolites in some plants. We tested the hypothesis that the effects of mycorrhization in ‘aroeira’ can be maximized by the application of P. The dry matter and the concentration of metabolites were evaluated. Mycorrhization increased the accumulation of phytomass, which was also favored at the highest dosage of P tested. The production of phenols and total proteins was maximized by mycorrhization only at an intermediate dosage of P. The inoculation did not favor the synthesis of flavonoids and soluble carbohydrates. The production of proanthocyanidins was influenced only by phosphate supplementation. It is concluded that the mycorrhization of seedlings of ‘aroeira-do-sertao’ associated with P fertilization maximizes the production of total phenols and total foliar proteins, making the phytomass more attractive to the herbal industry and resulting in the use of P fertilization.

Journal ArticleDOI
TL;DR: Although the canopy leaves of P. hederaceum exhibited a limited improvement in light foraging capacity, the species’ construction and maintenance costs are expected to be lower than those of its sympatric heteromorphs and allomorphs.
Abstract: Lianescent aroids grow horizontally while on the ground (shaded, humid habitats), but switch to vertical growth when they reach a host (exposed, desiccant habitats). There are three morphotypes with respect to leaf adjustment to canopy conditions: isomorphic, allomorphic, and heteromorphic. Allomorphs and heteromorphs exhibit marked leaf modifications (e.g., leaf area) that have a strategic effect on the plant’s carbon balance, since they increase its light foraging capacity in the canopy. Isomorphs do not show external leaf morphology modifications. Therefore, we hypothesized that leaf anatomy and physiology change instead, allowing their light foraging capacity to improve while they grow towards the canopy. We evaluated leaf area, lamina-specific mass, mesophyll anatomy, venation density and thickness, stomatal density, chlorophyll concentration and fluorescence in leaves of the isomorph Philodendron hederaceum, grown to three heights (terrestrial, 1.5 and 3 m). Stomatal density, chlorophyll a content, and electron transport rate were significantly higher in the canopy leaves (60, 54, and 50%, respectively). Thus, P. hederaceum exhibits leaf adjustments that enhance its light foraging capacity. However, these changes are relatively less marked than those exhibited by sympatric heteromorphs and allomorphs. Although the canopy leaves of P. hederaceum exhibited a limited improvement in light foraging capacity, the species’ construction and maintenance costs are expected to be lower than those of its sympatric heteromorphs and allomorphs. Future studies that consider leaf lifespan will add another perspective for understanding the costs and benefits of these growth habits in aroid vines.

Journal ArticleDOI
TL;DR: The growth inhibitory results of this study suggest that trans-ferulaldehyde may be responsible for the inhibitory effects of E. atropurpurea and may contribute to weed allelopathy.
Abstract: Plants, which include crops, weeds, and trees, are able to release effective allelochemicals that inhibit the growth and development of other plants. Eleocharis atropurpurea, a small, annual tufted weed, is renowned for being widely found in crop fields, yet there have been no studies on the allelopathy of E. atropurpurea (Cyperaceae). Thus, we explored the allelopathic potential and allelochemicals in E. atropurpurea and found that aqueous methanol extracts of E. atropurpurea inhibited the seedling growth of Lepidium sativum, Medicago sativa, Lolium multiflorum, and Phleum pratense. There was a significant negative correlation between the seedling growth of the test plants and extract concentration. Extracts were purified using several chromatographic steps and one growth inhibitory substance was isolated and identified by spectroscopic analysis as trans-ferulaldehyde. The active substance trans-ferulaldehyde significantly inhibited the shoot and root length of Lepidium sativum at concentrations higher than 1.0 and 3.0 mM, respectively, whereas the seedling length of Echinochloa crus-galli was inhibited by trans-ferulaldehyde at concentrations higher than 3.0 mM. The trans-ferulaldehyde I50 values for the growth of Lepidium sativum and Echinochloa crus-galli were in the range of 0.73–3.68 mM. The growth inhibitory results of this study suggest that trans-ferulaldehyde may be responsible for the inhibitory effects of E. atropurpurea and may contribute to weed allelopathy.

Journal ArticleDOI
TL;DR: In this article, the ability of Citrus roots to redistribute water is genotype-dependent and may be an important physiological mechanism associated with drought tolerance in Citrus rootstocks.
Abstract: Hydraulic redistribution could contribute significantly to plant water balance under limiting conditions, reducing plant sensitivity to drought. We hypothesized that citrus species are able to redistribute water under drought, transporting water from a wet to a dry portion of root system. Using an unusual experimental design, ‘Rangpur’ lime and ‘Swingle’ citrumelo rootstocks were inarched into Valencia sweet orange trunk and subjected to water withholding. In a split root system, each plant was composed by two rootstocks, isolated from each other. During water deficit, only one rootstock faced low water availability while the other remained well watered. Sap flow, leaf water potential and soil moisture were monitored for 42 days. We found reserve sap flow in both rootstocks, with water being transported from the irrigated rootstock to the non-irrigated one. Nocturnal sap flow of well-watered rootstocks revealed that water redistribution continued at night, with ‘Rangpur’ lime showing higher hydraulic redistribution than ‘Swingle’ citrumelo. The ability of Citrus roots to redistribute water is genotype-dependent and may be an important physiological mechanism associated with drought tolerance in Citrus rootstocks.

Journal ArticleDOI
TL;DR: In this article, the effect of soil water deficiency on other physiological traits has been investigated in Amazonian trees, including leaf pigment content, gas exchange, chlorophyll fluorescence, total leaf area (AL), consumptive use of water (CUW, total amount of water used for irrigation), and biomass accumulation.
Abstract: A reduction in rainfall is predicted by climate models for some parts of the Amazon, and a decline in stomatal conductance (gs) is often the main effect of drought. The physiological effect of soil water deficit on other physiological traits has been little investigated in Amazonian trees. In this work we assess the effect of soil water deficit on leaf pigment content, gas exchange, chlorophyll fluorescence, total leaf area (AL), consumptive use of water (CUW, total amount of water used for irrigation), and biomass accumulation. Plants of Garcinia brasiliensis were grown in pots under greenhouse conditions and submitted to soil water deficit for 90 days, when several physiological parameters were measured. Water deficit was induced by reducing soil water content (SWC) to 25, 50 and 75% of field capacity (FC). The control was soil at 100% FC. Midday leaf water potential varied from − 0.72 MPa (SWC at 25% FC) to − 0.29 MPa in well-irrigated plants. Subjecting the plants to soil water deficit did not affect light saturating photosynthesis, leaf pigment content, Ribulose-1,5-biphosphate carboxylase/oxygenase (Rubisco) activity or fluorescence parameters. Under moderate water stress Garcinia plants did not reduce stomatal conductance (gs) which remained rather unchanged. Instead, we found that mild water stress led to an increase in total non-structural carbohydrates, and as the stress progressed AL substantially declined, at a SWC of 25% FC. Drastic reduction of AL in plants exposed to SWC of 25% FC contributed to a reduction in total biomass accumulation, and a drop in AL resulted in a decline in CUW in this treatment. These results show that although there is no effect of moderated water stress on photosynthesis, gs or photochemical responses, there is a remarkable effect of moderate drought on biomass accumulation.

Journal ArticleDOI
TL;DR: In this article, the authors proposed that the background flow is affected by the radial water flow and tissue capacitance, which is fundamental for understanding plant water transport, the coupling between the phloem and xylem, and water relations under drought conditions.
Abstract: Despite the importance of water transport efficiency for plant productivity, the current methods to measure the hydraulic conductance in stem segments are limited and can be tricky. These measurements may be unstable for several hours and there are no satisfactory procedures that allow choosing the moment to get reliable measures. Such instability may be generated by background flow, when there is a flow even without applying water pressure to induce the axial flow. Underlying mechanisms related to background flow are still unknown and based on available literature, we propose that the background flow is affected, or even explained, by the radial water flow and tissue capacitance. For this reason, both phenomena are fundamental for understanding plant water transport, the coupling between the phloem and xylem, and water relations under drought conditions. Besides addressing this issue, we suggest ways to study the radial water flow and capacitance in stem segments.

Journal ArticleDOI
TL;DR: The interesting finding was that drought decreased 2S albumin expression in this species, which possibly will lower the allergenic reactivity and could enhance the feed value of M. oleifera for human health.
Abstract: An experiment was conducted to explore the effect of water deficit on 2S albumin gene expression in Moringa oleifera with a predication of its allergenic reactivity. Drought was applied to 20-day-old plants for 1 month by limiting the irrigation water to half the control level. Soil water content and plant relative water content of drought treatment were about 50 and 70% of control values, respectively at the end of the stress period. Additionally, in relation to the control plants, drought reduced plant height (− 34%), leaf number (− 16%), total plant biomass (− 60%), shoot dry mass (− 37%) and root dry mass (− 21%). Conversely, root/shoot ratio was enhanced due to this stress. Quantitative polymerase chain reaction (qPCR) results revealed that drought enormously reduced 2S albumin gene expression in leaves and roots. Under control conditions, the relative albumin gene expression in roots was about half that of the leaves. Paratope and epitope prediction showed that albumin 31 which is a member of 2S albumin family, has eight cysteine residues and 25% of solvent-exposed regions. This makes albumin 31 a proposed target for food allergy investigations. Our interesting finding was that drought decreased 2S albumin expression in this species. This possibly will lower the allergenic reactivity and could enhance the feed value of M. oleifera for human health.

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TL;DR: In this paper, the responses of full sun-light exposed (FSE) leaves, leaves at intermediate position (IP) and shaded leaves (S) of three Passiflora genotypes [P. edulis f. flavicarpa (M); P. giberti (G) and P. cincinnata (C)].
Abstract: Passion fruit plants (Passiflora spp.) have very dense canopies so that leaves located at the top of them can shade the ones more internally located. This shade can change physiological and morphological leaf traits. Here we used gas exchange and chlorophyll a fluorescence parameters as tools to evaluate the responses of full sun-light exposed (FSE) leaves, leaves at intermediate position (IP) and shaded leaves (S) of three Passiflora genotypes [P. edulis f. flavicarpa (Maguary selection—FB 100) (M); P. giberti (G) and P. cincinnata (C)]. FSE leaves presented greater net photosynthetic rates (A net ), what accounted for increasing both intrinsic water use efficiency and water use efficiency. Otherwise, leaves grown and adapted to shade environments tended to always show low A net values, although such values were increased at 12:00, when light availability was improved. Leaves at IP and S leaves presented higher ratio of internal to ambient CO2 concentration (C i /C a ) likely due to reduced carboxylation efficiency. FSE leaves presented photoprotection mechanisms against high light intensities, while leaves under lower light intensities (IP and S) showed variable responses of chlorophyll a fluorescence, depending on the genotype.

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TL;DR: In this article, the photochemical response of 18 Eucalyptus species, one Corimbia and one hybrid subjected to low temperature using two chilling treatments was compared, based on chlorophyll fluorescence parameters.
Abstract: Eucalyptus plant is one of the most economic important forest species explored worldwide and in some countries its cultivation is expanding to regions with lower temperatures, including Brazil. This study aimed to compare the photochemical response of 18 Eucalyptus species, one Corimbia and one hybrid subjected to low temperature using two chilling treatments. Six-month-old plants were exposed to (1) gradual chilling (20–0 °C in four steps of 5 °C for 10 min) and abrupt chilling (20−5 °C in one step). Based on chlorophyll fluorescence parameters, eucalyptus species responded differently depending on how chilling was applied. E. tereticornis presented the best performance under chilling, regardless how it was imposed. The effective quantum yield of photosystem II was the best parameter to identify variation in photochemical responses of eucalyptus species to chilling. It was also observed that E. brassiana, C. citriodora, E. grandis, E. gunni, and E. resinifera were sensitive to the way chilling was applied, leading to differential photochemical response.

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TL;DR: In this article, a gel-free/label-free proteomic analysis was conducted to understand physiological processes in seeds under temperature stress, which affects quality of stored buckwheat grain.
Abstract: Buckwheat is a functional staple food, which is rich in rutin and other flavonoids with strong antioxidant potential. However, the quality of buckwheat grain is easy to degrade during storage and low temperature is better to keep the flavor and texture. We tested the hypothesis that the quality degradation is related to seed dormancy which is lost at a rate in temperature-dependent manner in most seeds. To understand physiological processes in seeds under temperature stress, which affects quality of stored buckwheat grain, a gel-free/label-free proteomic analysis was conducted. Compared to the seeds before storage, a total of 30, 76, 52, 14, and 61 proteins were affected at 5 °C for 5 months, 5 °C for 10 months, 15 °C for 5 months, 15 °C for 10 months, and 25 °C for 5 months, respectively. Functional classification revealed that storage condition at 5 °C for 5 months resulted in different protein profile from other conditions and suitable for keeping best condition. Storage at higher temperature for longer time influenced proteins related to preparation for emergence by carbohydrate metabolism, endogenous gene expression, and protein homeostasis. Proteins such as granule-bound starch synthase and 13S seed storage protein consistently decreased in abundance during storage. These results suggest that stored buckwheat seeds experience seed dormancy release, but the processes are not clear in relation to temperature rise. Dormancy break is recognized but emergence is inhibited by abscisic acid, which was induced by temperature stress, showing the complexity of buckwheat germination control. The quality degradation of stored seeds might be due to changed starch composition and protein network.

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TL;DR: In this article, the effects of soil water deficit and rewatering on leaf water potential (ψleaf), gas exchange and chlorophyll fluorescence emission in peach palms were evaluated.
Abstract: The Amazonian peach palm is presently the main species of heart-of- palm producer in many Brazilian regions. Here we evaluated the effects of soil water deficit and rewatering on leaf water potential (ψleaf), gas exchange and chlorophyll fluorescence emission in peach palms. Plants were grown in 80 L-plastic pots under greenhouse conditions. Water deficit was imposed by water withdrawing for 13 days, when irrigation was re-established for 8 days more. ψleaf was measured at 5:30 a.m. and 1:30 p.m. Gas exchange measurements were performed at 8:00 a.m. and at 2:00 p.m., after chlorophyll a fluorescence evaluations. The minimum ψleaf value observed at predawn was − 1.6 MPa, when net CO2 assimilation (PN) was zero on the 13th day of water deficit, thus showing mesophytes characteristics. The sharp PN decrease of 94%, 6 days after the beginning of treatments, demonstrated the drastic effect of the soil water deficit. After rewatering, a rapid recuperation of ψleaf was observed, whereas PN, transpiration rate (E) and stomatal conductance (gs) recovered more slowly, reaching values exhibited by the control plants only 7 days after rewatering. The lower maximal quantum yield of photosystem II (PSII) (FV/FM) values in the midday for plants under water deficit indicated dynamic photoinhibition of PS II to excessive PPFD. These results suggest a drought tolerance of peach palm plants, showing stomatal control of water losses and PN limitation, whereas the photosynthetic apparatus was maintained by photoprotection processes.

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TL;DR: It is shown that ABCF3 regulates stress response by modulating aquaporin gene expression and ER stress responses in Arabidopsis through regulating H2O2 uptake and endoplasmic reticulum stress responses.
Abstract: The ATP-binding cassette (ABC) F/GCN (general control non-derepressible) subfamily is a group of soluble ABC proteins that has two nucleotide binding domains (NBDs) but no transmembrane domains (TMDs). Previous study has indicated that ABCF3, also called GCN20/SCORD5, is involved in stress-associated protein translation control and defense responses to bacterial infection. Here, we show that ABCF3 regulates H2O2 uptake and endoplasmic reticulum (ER) stress responses in Arabidopsis. ABCF3 expressed mainly in leaves, stems, root tips, seeds, and anther. Analysis of abcf3 mutants and transgenic overexpressors (OX) of ABCF3 indicates that ABCF3 regulates H2O2 uptake. qRT-PCR analysis indicated that ABCF3 affects the expression of several aquaporin genes that were involved in H2O2 uptake in plants. In addition, abcf3 mutants exhibited enhanced sensitivity to ER stress and amino acid deprivation when challenged with ER stress inducers tunicamycin and amino acid synthesis inhibitor chlorsulfuron compared to wild type. Overexpression of AtABCF3 increases, whereas, abcf3 mutants depress the expression of ER stress-related genes. Taken together, these results indicated that ABCF3 regulates stress response by modulating aquaporin gene expression and ER stress responses.

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TL;DR: In this paper, the effects of UV-B irradiation and Biomin (a natural substance extracted from coal with active ingredients of Humic acids) on the content of endogenous polyamines spermine, spermidine and putrescine, and free amino acids in shoots and roots of young triticale seedlings were investigated.
Abstract: The effects of UV-B irradiation and Biomin (a natural substance extracted from coal with active ingredients of humic acids) on the content of endogenous polyamines spermine, spermidine and putrescine, and free amino acids in shoots and roots of young triticale seedlings were investigated. Biomin was added to the nutrient medium 3 days prior to UV-B irradiation. The seedlings were treated with 7.7 kJ m−2 day−1 UV-B light for 4 days. The exposure to UV-B increased total free amino acids, while Biomin application alone did not affect considerably their content. The treatment with UV-B or Biomin alone provoked augmentation of conjugated and bound polyamine (PA) fractions. Data suggest that Biomin alleviates the negative consequences of UV-B stress, manifested by the normalized amino acid and polyamine amounts in the UV-B + Biomin-treated plants. This study demonstrates the protective effect of Biomin on triticale plants against UV-B irradiation, which could be related to alterations in PAs and amino acids pools.

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TL;DR: In this article, the authors examined the hypothesis that leaf gas exchange of scion is affected by different rootstocks in wood plants and concluded that grafting might affect the photosynthetic metabolism of the atemoya hybrid, regardless of the combination used.
Abstract: We examined the hypothesis that leaf gas exchange of scion is affected by different rootstocks in wood plants. We investigated daily courses of gas exchange and photosynthetic potential using the CO2 assimilation rates as a function of photosynthetic photon flux density, and then assessed CO2 response curves in atemoya scion (Annona × atemoya Mabb.) grafted onto araticum-de-terra-fria [A. emarginata (Schltdl.) H. Rainer var. terra-fria]: ATF, araticum-mirim [A. emarginata (Schltdl.) H. Rainer var. mirim]: ATM, biriba [A. mucosa (Bail.) H. Rainer]: ATB, atemoya (autograft): ATA, and in ungrafted atemoya plants: CTR. Throughout the entire evaluation period, the net assimilation rate (Anet) and stomatal conductance (gs) of CTR plants remained practically constant, being lower than those of grafted plants between 08:00 a.m. and 12:00 a.m., regardless of the rootstock used. Moreover, ATM plants proved to be more efficient in keeping the stomata open, even during the hottest hours of the day, improving Anet and carboxylation use efficiency. However, this occurred at the lowest maximum carboxylation rate of ribulose-1,5-bisphosphate (Vcmax). Overall, ATF plants presented a low light saturation point and photosynthetic electron transport rates, though increased maximum quantum yield of photosynthesis was observed. Thus, we accept our hypothesis and conclude that grafting might affect the photosynthetic metabolism of the atemoya hybrid, regardless of the combination used, which promotes enhanced Anet and low Vcmax and light saturation points.

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TL;DR: In this article, the authors analyzed the photosynthetic performance (parameters derived of chlorophyll fluorescence), chlorophyLL a concentrations and the content of UV-absorbing compounds (mycosporine-like aminoacids) in three tropical lotic macroalgae, Cladophora glomerata (Chlorophyta), Spirogyra sp. (Streptophyta) and Sirodotia delicatula (Rhodophyta).
Abstract: Freshwater algae inhabiting shallow waters are most effectively affected by UV radiation. The aim of this study was to analyze the photosynthetic performance (parameters derived of chlorophyll fluorescence), chlorophyll a concentrations and the content of UV-absorbing compounds (mycosporine-like aminoacids—MAAs) in three tropical lotic macroalgae, Cladophora glomerata (Chlorophyta), Spirogyra sp. (Streptophyta) and Sirodotia delicatula (Rhodophyta) in response to UV radiation exposure under laboratory conditions. Experiments were performed under three treatments: (1) PAR (400–700 nm), P; (2) PAR + UVA (320–700 nm), PA; (3) PAR + UVA + UVB (280–700 nm), PAB. Cladophora glomerata and Spirogyra sp., typical sun-adapted lotic macroalgae, had distinct responses to UV radiation exposure. A more pronounced decrease of Fv/Fm and increase of NPQ under UVA than UVAB was observed, whereas chlorophyll a content was lower under UVAB in C. glomerata. Spirogyra sp. had a decrease of photosynthetic yields (ΔF/Fm′ and Fv/Fm) under PAR, indicating that UVAB radiation may have a positive effect on the photosynthetic apparatus. Surprisingly, S. delicatula, a shade-adapted alga, exhibited less sensitivity to UV exposure. These results suggest that the presence of MAAs (shinorine and palythine) in S. delicatula is a significant shield of protection against UV radiation.